The present invention relates to an elastomeric damping device especially for the neck of helicopter wing blades. More specifically, the invention relates to a damping device for a rotor blade capable of vibrations having a blade neck which is relatively flexible or soft against bending in the lead-lag direction of the blade.
U.S. Pat. No. 4,097,193 assigned to the same assignee relates to an elastomeric damping arrangement constructed to provide a highly efficient damping of the vibrations of a vibration prone member, such as an airfoil, especially a helicopter rotor blade. The prior art damping arrangement is applied directly on or to the vibration prone structural member in the region of dynamic deformations as an integral component of the structural member. At least one damping layer is covered by a protecting outer layer which merges smoothly into the surface of the vibration prone member. The damping layer is made of a visco-elastic material having a high internal damping action. The protecting cover layer is made of high strength material having a high rigidity in the direction of the occurring damping force. Such structure leaves room for improvement, especially with regard to the efficiency of the damping action.
U.S. patent application Ser. No. 015,311, filed Feb. 26, 1979, now in condition for allowance and also assigned to the same assignee as the present application, relates to a rotor blade especially for rotary wing aircraft in which the rotor blade has a neck connecting the blade proper to a rotor head at the blade root. The neck section is flexible against bending in the lead-lag direction and in the flapping direction. A carrier member is located alongside or inside the neck section, but spaced from the neck section. The carrier member is resistant against bending at least in the lead-lag direction or in the flapping direction. The carrier member is rigidly connected at its one end to the blade proper. A layer of a damping material is operatively interposed between the carrier member and the neck section, preferably at the blade root end of the neck section, whereby blade vibrations preferably in the lead-lag direction are damped and substantially prevented from entering into the rotor head. Such a structure also leaves room for improvement, especially with regard to achieving a more effective damping action with simpler means.